Bucking at running temperature

Hi Amber,

It appears there is only one option for transmission in this vehicle which is a CVT transmission. Is that what you have? Continuously Variable Transmission.

Next do you have a 4 wheel drive vehicle or an AWD vehicle? The difference is, 4WD can be put in 2WD, 4HI, 4LO or if you have an auto 4WD (All Wheel Drive) then it is always in 2WD until the computer determines when it needs 4WD and it puts it in by itself.

If you have AWD or Auto 4WD, have you replaced any of your tires without replacing all 4? Meaning did you get a nail or a flat and replace one tire, or just replace two tires at a time?

Can you confirm this is the transmission and other questions and we can go from there because I think I know exactly what this is depending on these answers. Thanks

Okay. There are three major things that this could be.

1. Due to the DTC P0420, it could be a misfire that is damaging the converter causing it to not reduce the emission like it should and it sets this code. However, this code could be set due to a faulty o2 sensor as well so we need to diagnose this by monitoring the short term fuel trim and see if the exhaust has excessive fuel in it. This would point to a misfire causing the issue.

Let me know if you have replaced the sensor and what the short term fuel trim is and we can go from there.

2. Due to this being an AWD there is a possibility that the transfer case is slipping when it is engaging and disengaging. This would be caused by mismatched tire sizes. However, if you always changed all 4 tires at the same time, this is unlikely.

If this is your issue then most likely the transfer case will need to be rebuilt or replaced. The way you figure this out is by using a scan tool and monitor the output shaft speed and clutch slippage and see if the feeling happens when the clutch is slipping and it doesn't match your output shaft speed.

3. Due to this being a CVT transmission they have a steel belt that connects the main two pulleys that transmit the power from the engine to the drive axles. As these transmissions begin to age, this steel belt actually slips causing a jerking/bucking feeling. I have also heard it described as a fish bite. If you have ever been fishing and you get a fish that nibbles on the bait and you feel that through the fishing pole. You will see the RPM jump and normally feel it under load like when you are accelerating. Here is a video that describes a CVT and actually shows you the steel belt. I suspect this is your issue that you are feeling and the converter code that you are getting is a separate issue.

https://youtu.be/PEq5_b4LWNY

If this is the issue, there are some places that will attempt to rebuild CVT transmissions but most places just replace them.

Let me know what you think and we can go from there. Thanks

Thanks Amber. I did not see that before. That is not very drastic but if the jerking sensation corresponds with this then I think you are at the beginning of the belt slipping. Before, you condemn it we should have the other two theories tested because they will be pretty definitive if they are the cause.

Again, I am not seeing anything to make me think it is not the steel belt slipping but it is the most intrusive thing so we need to leave it to last.

Okay. The torque convert can be replaced cheaper than replacing the unit. If you want I would seek a second opinion. However, if I was correct that it is the steel belt which gets misdiagnosed all the time and mistaken for the torque converter, replacing the unit would be a better option.

Either way if they replace the unit you will get both a torque converter and steel belt so I am sure it will fix it.

Thanks for the update. Please let me know if you need anything else.